1. Field of the Invention
With this type of endoscope it is possible to carry out for example minimal invasive therapeutic or diagnostic interventions. It is also possible to employ this endoscope for example in technical endoscopy as a so called technoscope.
2. Description of the Related Art
These endoscopes include a shaft to be introduced into a hollow space, on the proximal end of which the image is projected by means of a special optical system, preferably a rod lens system, onto a lens situated in an eyepiece. The image of the area of operation or the hollow space to be viewed produced in this manner is displayed on a monitor by means of an associated camera or a signal divider and control unit (camera controller).
Generally the illumination light is conducted from an external light source along a light guide comprised of a fiber bundle or a liquid guide to the endoscope, and from is coupled to additional light guides provided in the inside of the endoscope, which internal light guides conduct light to the distal end of the endoscope.
This conventional illumination system is technically complex. The conventionally employed cold light sources, for example xenon- or halogen lights, require a relatively high electrical power and require technically complex measures for wiring and for cooling, in order to supply sufficient light to the distal end of the endoscope even in the case of long light guides and high transmission or coupling losses. Also, the above mentioned light sources do not have an optimal efficiency.
In addition there is a high failure rate due to the short life span of these light sources and the high mechanical stresses to which the light bundles are subjected, which results in high maintenance costs and therewith a reduction in the economic justifiability.
From DE 296 13 103 U1, DE 298 12 048 U1 endoscopes are known in which light emitting diodes, so called LED""s, are provided at the distal end of the endoscope as the illumination source.
The advantage of providing the illumination source at the distal end is that coupling losses between the light guides and transmission losses through the long light guides can be avoided. Further, a CCD-Chip (Charge Coupled Device-Chip) can be provided at the distal end of the endoscope as image receiver, whereby image light intensity losses consequent to air or glass transmission can be avoided.
In DE 296 13 103. U1 the use of LED-Chips is proposed for the representation of the colors red, blue and green to take advantage of the fluorescence excitation produced by fluorescent materials which collect in carcinogenic tissue. This use makes it necessary to use a chip with CCD-elements for black-white transmission, wherein a dichroic filter with a transmissivity of  greater than 56 nm must be interposed. This arrangement, in particular the use of the mentioned black-white-CCD, however, substantially reduces the possible areas of employment of the endoscope.
In DE 299 10 795 U1 an endoscope is described, in which multiple illumination units are provided axially sequentially on the shaft, wherein light is supplied through light guides via arrays of LED""s situated at the proximal end. This arrangement requires greater amounts of energy, due to the increased amount of light produced by the greater number of illumination units employed in the total system and the losses due to the coupling in of the individual illumination units in the light guides. Besides this, the coupling in of the light guides and their incorporation in a shaft is complex in thus very expansive.
The present invention is based on the task of providing an endoscope in which the operation and ergonomics are improved and with which the manufacturing costs are reduced through the improvement in the integration of the illumination system. Besides this the outer diameter of the endoscope shaft should be as small as possible.
It is the basic idea of the invention to use, as illumination devices, LED""s on ring shaped, light transmissive carriers, in the following also referred to as illumination rings, which are provided between the inner and outer sheath tube, that is, surrounding the optics, wherein multiple carriers are provided axially, cascade-like, sequentially between the proximal and distal end of the shaft in the ring space between inner and outer sheath pipe.
With an arrangement of this type a substantially greater light density is produced than with known endoscopes of this type. Glass fiber light guides in the inside of the shaft pipe can be completely dispensed with.
Thereby the manufacturing is simplified and costs are reduced, and a very narrow shaft diameter can be realized.
The LED""s forming the illumination units can be bonded to carriers in the form of ring-shaped glass discs, that is, mechanically wired, and the conductor circuits for supplying current to the LED""s can be produced by vapor deposition, preferably gold vapor deposition. Thereby a significantly greater manufacturing density achieved, which cannot be achieved with conventional premanufactured LED""s or with SMD LED""s (Surface Mounted Device-LED""s).
A further increase in the light density can be achieved thereby, that a mirror reflecting the light is provided behind the proximal last carrier, which can be comprised of a vapor deposited metal layer. The idea serves the same purpose, wherein the opposing or facing surfaces of the inner and outer sheath pipe, between which the carrier with the LED""s is provided, is entirely or partially provided with a reflective layer.
In known manner the distal end of the shaft is closed of with a light transmissive plate or even with a lens.
Further means for economical production of the carrier for the light units are set forth.
The supply of current for the LED""s can occur, via an electrical supply circuit, which extends in the ring space between inner and outer hollow space, and which is electrically connected via a plug-in contact. In this plug-in contact a plug adapted for supplying current can be plugged in. Thereby the endoscope can be connected and disconnected in a very simple manner.
A contactless current supply for the LED""s is possible, when the electrical supply lines are connected with a induction coil provided in the lens or optics. Current can be produced in this coil by a contactless surrounding, magnetic field producing induction coil, which current is supply to the LED""s.
By this means the manipulability, and above all the ability to clean, in particular the ability to sterilize in an autoclave, are further improved.
Alternatively, in a parallel wiring of the LED""s the sheath pipe can also be employed as conductor. In the case of soldering the light rings with the sheath pipe, this can be used to advantage for conducting away heat.
By dispensing with external light sources, as well as the light cable connecting these with the endoscope, the manufacturing and maintenance costs of this type of system are reduced. Supply costs for light cables and gas discharge lamps are dispensed with, the need for repairs is reduced, which results in a very high reliability of the system.
Besides white emitting LED""s, monochromatic emitting LED""s can be employed. In this case, by wave convection by means of the red, green and blue light emitted by the LED""s white light can be produced, in that the complementary colors are mixed in a particular relationship.
Means for image reproduction are set forth.